/**
 * Copyright (C) 2009-2011 Couchbase, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALING
 * IN THE SOFTWARE.
 */

package com.nepxion.thunder.cluster.loadbalance.consistenthash.ketama;

import java.util.Iterator;
import java.util.TreeMap;

/**
 * Implements an Iterator which the KetamaNodeLoctaor may return to a client for
 * iterating through alternate nodes for a given key.
 */
class KetamaIterator<T> implements Iterator<T> {

    private final String key;
    private long hashVal;
    private int remainingTries;
    private int numTries = 0;
    private final HashAlgorithm hashAlg;
    private final TreeMap<Long, T> ketamaNodes;

    /**
     * Create a new KetamaIterator to be used by a client for an operation.
     *
     * @param k
     *            the key to iterate for
     * @param t
     *            the number of tries until giving up
     * @param ketamaNodes
     *            the continuum in the form of a TreeMap to be used when
     *            selecting a node
     * @param hashAlg
     *            the hash algorithm to use when selecting within the continuumq
     */
    protected KetamaIterator(final String k, final int t, TreeMap<Long, T> ketamaNodes, final HashAlgorithm hashAlg) {
        super();
        this.ketamaNodes = ketamaNodes;
        this.hashAlg = hashAlg;
        hashVal = hashAlg.hash(k);
        remainingTries = t;
        key = k;
    }

    private void nextHash() {
        // this.calculateHash(Integer.toString(tries)+key).hashCode();
        long tmpKey = hashAlg.hash((numTries++) + key);
        // This echos the implementation of Long.hashCode()
        hashVal += (int) (tmpKey ^ (tmpKey >>> 32));
        hashVal &= 0xffffffffL; /* truncate to 32-bits */
        remainingTries--;
    }

    public boolean hasNext() {
        return remainingTries > 0;
    }

    public T next() {
        try {
            return getNodeForKey(hashVal);
        } finally {
            nextHash();
        }
    }

    public void remove() {
        throw new UnsupportedOperationException("remove not supported");
    }

    private T getNodeForKey(long hash) {
        final T rv;
        if (!ketamaNodes.containsKey(hash)) {
            // Java 1.6 adds a ceilingKey method, but I'm still stuck in 1.5
            // in a lot of places, so I'm doing this myself.
            /*SortedMap<Long, T> tailMap = ketamaNodes.tailMap(hash);
            if (tailMap.isEmpty()) {
                hash = ketamaNodes.firstKey();
            } else {
                hash = tailMap.firstKey();
            }*/
            
            Long newHash = ketamaNodes.ceilingKey(hash);  
            if (newHash == null) {
                hash = ketamaNodes.firstKey();
            } else {
                hash = newHash.longValue();
            }
        }
        rv = ketamaNodes.get(hash);
        return rv;
    }
}